Abstract promises are commonly bandied around about cloud services, but the 10,000-feet view leaves out the crucial detail about the realities of shifting an IT infrastructure to a cloud service.

The CIO of BP Dana Deasy detailed the challenges that multinational oil giant has faced during its foray into cloud services.

By the end of this year email for more than 83,000 BP employees will be served from a private cloud that scales based on demand, following the migration of its Microsoft Exchange servers. The company also uses a variety of software as a service (SaaS) and infrastructure as a service (IaaS) providers to support its intranet and public facing site BP.com.

Getting these services up and running has challenged Deasy, who identified several key issues that companies embarking on a similar journey should be aware of.

"Along the way things don't always go right," he said, "you run into obstacles where you say 'We hadn't planned on that'".

Don't expect one vendor to do it all

Chances are there won't be one cloud service provider that can meet your needs at each level of the cloud software and hardware stack, said Deasy at the recent Cloud World Forum event in London.

BP relies on nine cloud service providers to provide a mix of IaaS and SaaS to serve hundreds of its intranet and public facing web sites.

"We wanted best-of-breed cloud solutions for every feature, but there is no single provider that can offer the best technological solution for each of our needs," said Deasy. "It is difficult to pick one service that fits all use cases.

"This can be very contrary to traditional IT where there can be a bias towards trying to find a platform that can do it all for you."

Cloud services won't play nice with legacy

"In a perfect world our legacy would sit in a box and connect with nothing else, we would be able to take stuff move it to the cloud and say 'That will never connect to legacy', but that's not how the real world works," said Deasy.

"If you have a migration strategy where you want to get an entire application and everything connected to it to the cloud, but it's going to take months or years to do that, how do you deal with the idea that some [of the system] is going to be bridged from the outside and some of it's going to live on the inside?"

Be prepared to ask for more money

"[You have to] sit in front of the CFO and say 'This cloud is really a good thing but while I'm getting there I might have some parallel running costs'. That's always a difficult and challenging conversation to have," said Deasy.

He said the company is looking at "how we start to take this very large fixed asset base and start to consolidate knowing that you're going to have parallel running costs and you're going to have to connect your legacy into the future".

Your in-house IT team need to be prepared for change

"Bringing your IT organisation along on this journey you is incredibly important," said Deasy.

CIOs need to understand and communicate to IT staff how the shift to cloud services will affect the department's role he said, for instance the move from directly supporting IT to brokering cloud services.

Can you do cloud at scale?

You may have successfully trialled a cloud service but the next step is ramping that up in a manageable way.

"Now that we've put some small stuff out there. How would you look at industrialising this, so that allows you to say 'I don't want to do half a dozen projects on the cloud at once, I want to do 100 projects on the cloud at once'", he said.

"How would you go about putting in the rules of the road that allows a company to do that in a way that you won't wake up one day say 'Why is it we suddenly have 500 different cloud providers, why is it we're using everybody out there' as opposed to a subset of the ones who make sense for us?"

About Nick Heath

Nick Heath is chief reporter for TechRepublic UK. He writes about the technology that IT-decision makers need to know about, and the latest happenings in the European tech scene.